package org.jgroups.protocols;
import org.jgroups.Address;
import org.jgroups.Event;
import org.jgroups.View;
import org.jgroups.ViewId;
import org.jgroups.annotations.*;
import org.jgroups.stack.Protocol;
import org.jgroups.util.TimeScheduler;
import org.jgroups.util.Util;
import java.util.*;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
/**
* Protocol to discover subgroups; e.g., existing due to a network partition (that healed). Example: group
* {p,q,r,s,t,u,v,w} is split into 3 subgroups {p,q}, {r,s,t,u} and {v,w}. This protocol will eventually send
* a MERGE event with the coordinators of each subgroup up the stack: {p,r,v}. Note that - depending on the time
* of subgroup discovery - there could also be 2 MERGE events, which first join 2 of the subgroups, and then the
* resulting group to the last subgroup. The real work of merging the subgroups into one larger group is done
* somewhere above this protocol (typically in the GMS protocol).<p>
* This protocol works as follows:
* <ul>
* <li>If coordinator: periodically retrieve the initial membership (using the FIND_INITIAL_MBRS event provided e.g.
* by PING or TCPPING protocols. This list contains {coord,addr} pairs.
* <li>If there is more than 1 coordinator:
* <ol>
* <li>Get all coordinators
* <li>Create a MERGE event with the list of coordinators as argument
* <li>Send the event up the stack
* </ol>
* </ul>
*
* <p>
*
* Requires: FIND_INITIAL_MBRS event from below<br>
* Provides: sends MERGE event with list of coordinators up the stack<br>
* @author Bela Ban, Oct 16 2001
* @version $Id: MERGE2.java,v 1.64 2009/06/12 09:58:34 belaban Exp $
*/
@MBean(description="Protocol to discover subgroups existing due to a network partition")
@DeprecatedProperty(names={"use_separate_thread"})
public class MERGE2 extends Protocol {
/* ----------------------------------------- Properties -------------------------------------------------- */
@ManagedAttribute(description="Minimum time between runs to discover other clusters", writable=true)
@Property(description="Lower bound in msec to run merge protocol. Default is 5000 msec")
private long min_interval=5000;
@ManagedAttribute(description="Maximum time between runs to discover other clusters", writable=true)
@Property(description="Upper bound in msec to run merge protocol. Default is 20000 msec")
private long max_interval=20000;
/* --------------------------------------------- Fields ------------------------------------------------------ */
private Address local_addr=null;
private View view;
private final FindSubgroupsTask task=new FindSubgroupsTask();
private volatile boolean is_coord=false;
private TimeScheduler timer;
public MERGE2() {
}
public void init() throws Exception {
timer=getTransport().getTimer();
if(timer == null)
throw new Exception("timer cannot be retrieved");
if(min_interval <= 0 || max_interval <= 0) {
throw new Exception("min_interval and max_interval have to be > 0");
}
if(max_interval <= min_interval) {
throw new Exception ("max_interval has to be greater than min_interval");
}
}
public String getName() {
return "MERGE2";
}
public long getMinInterval() {
return min_interval;
}
public void setMinInterval(long i) {
min_interval=i;
}
public long getMaxInterval() {
return max_interval;
}
public void setMaxInterval(long l) {
max_interval=l;
}
public Vector<Integer> requiredDownServices() {
Vector<Integer> retval=new Vector<Integer>(1);
retval.addElement(new Integer(Event.FIND_INITIAL_MBRS));
return retval;
}
/** Discovers members and detects whether we have multiple coordinator. If so, kicks off a merge */
@ManagedOperation
public void sendMergeSolicitation() {
task.findAndNotify();
}
public void stop() {
is_coord=false;
task.stop();
}
public Object down(Event evt) {
switch(evt.getType()) {
case Event.VIEW_CHANGE:
Object ret=down_prot.down(evt);
view=(View)evt.getArg();
Vector<Address> mbrs=view.getMembers();
if(mbrs == null || mbrs.isEmpty() || local_addr == null) {
task.stop();
return ret;
}
Address coord=mbrs.elementAt(0);
if(coord.equals(local_addr)) {
is_coord=true;
task.start(); // start task if we became coordinator (doesn't start if already running)
}
else {
// if we were coordinator, but are no longer, stop task. this happens e.g. when we merge and someone
// else becomes the new coordinator of the merged group
if(is_coord) {
is_coord=false;
}
task.stop();
}
return ret;
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
return down_prot.down(evt);
default:
return down_prot.down(evt); // Pass on to the layer below us
}
}
/**
* Task periodically executing (if role is coordinator). Gets the initial membership and determines
* whether there are subgroups (multiple coordinators for the same group). If yes, it sends a MERGE event
* with the list of the coordinators up the stack
*/
private class FindSubgroupsTask {
@GuardedBy("this")
private Future<?> future;
public synchronized void start() {
if(future == null || future.isDone()) {
future=timer.scheduleWithFixedDelay(new Runnable() {
public void run() {
findAndNotify();
}
}, 2500, computeInterval(), TimeUnit.MILLISECONDS);
}
}
public synchronized void stop() {
if(future != null) {
future.cancel(true);
future=null;
}
}
public void findAndNotify() {
List<PingData> initial_mbrs=findInitialMembers();
List<View> different_views=detectDifferentViews(initial_mbrs);
if(different_views.size() > 1) {
if(log.isDebugEnabled())
log.debug(local_addr + " found different views : " + Util.print(different_views) + "; sending up MERGE event");
Event evt=new Event(Event.MERGE, different_views);
try {
up_prot.up(evt);
}
catch(Throwable t) {
log.error("failed sending up MERGE event", t);
}
}
}
/**
* Returns a random value within [min_interval - max_interval]
*/
long computeInterval() {
return min_interval + Util.random(max_interval - min_interval);
}
/** Returns a list of PingData pairs */
@SuppressWarnings("unchecked")
List<PingData> findInitialMembers() {
PingData tmp=new PingData(local_addr, view, true);
List<PingData> retval=(List<PingData>)down_prot.down(new Event(Event.FIND_INITIAL_MBRS));
if(retval == null) return Collections.emptyList();
if(is_coord && local_addr != null) {
//let's make sure that we add ourself as a coordinator
if(retval.contains(tmp))
retval.remove(tmp);
retval.add(tmp);
}
return retval;
}
/**
* Finds out if there is more than 1 coordinator in the initial_mbrs vector (contains PingData elements).
* @param initial_mbrs A list of PingData pairs
* @return Vector A list of the coordinators (Addresses) found. Will contain just 1 element for a correct
* membership, and more than 1 for multiple coordinators
*/
List<Address> detectMultipleCoordinators(List<PingData> initial_mbrs) {
Vector<Address> ret=new Vector<Address>();
for(PingData response:initial_mbrs) {
if(response.isServer()) {
Address coord=response.getCoordAddress();
if(!ret.contains(coord))
ret.add(coord);
}
}
return ret;
}
List<View> detectDifferentViews(List<PingData> initial_mbrs) {
List<View> ret=new ArrayList<View>();
for(PingData response:initial_mbrs) {
if(!response.isServer())
continue;
View view=response.getView();
if(view == null)
continue;
ViewId vid=view.getVid();
if(!containsViewId(ret, vid))
ret.add(view);
}
return ret;
}
boolean containsViewId(Collection<View> views, ViewId vid) {
for(View view: views) {
ViewId tmp=view.getVid();
if(Util.sameViewId(vid, tmp))
return true;
}
return false;
}
}
}